The present invention relates to a method of creating, at the time of performing machining of a workpiece in accordance with an NC program, wear data of a tool used, estimating tool wear in necessary machining and judging whether a tool selected in relation to this machining may be used or not, and more particularly to an improved method of mutually associating machining and tool wear, estimating tool wear by an adaptively controlled simulation, comparing and calibrating this estimated wear as an actual measurement value and performing life control by comparing this wear with the life database of a tool.
Conventionally, at the time when machining a workpiece using an NC program, human beings have looked at a tool with their eyes, checked the state of the tool wear, forecast the life of the tool, discerned a cutting sound during machining or the surface roughness after machining and forecast the life. Then, from this forecast they have judged whether the tool is used or not. Further, in a machine tool controller having a tool life control function, the usability of the tool has been judged using the function. The conventional life control function has used a control method of estimating the life of a tool on the basis of only the cutting time, use frequency and cutting distance of the tool, counted the cutting time, use frequency and cutting distance of a tool being used, during machining on a real-time basis, judged that life was exhausted when the data reached a predetermined value and automatically performed such an operation as changing the used tool with another tool. Although the predetermined value is written in tool catalogs by a tool manufacturer based on test data under a certain condition, the data is not consistent under all cutting conditions and the value is merely an estimate.
Further, relying only on a forecast by a conventional worker, its criteria are ambiguous and even a skillful worker cannot accurately forecast the life. As a result, tool damage and chipping might have occurred during machining.
Furthermore, according to the life control function, if a predetermined value is standardized, it was possible to prevent tool damage to some extent with a fixed probability regardless of the level of skill of a worker. However, because a forecast is impossible, it cannot be prevented that useful life of the tool will run out during machining. As a result, in the same manner as before, tool damage and chipping might have occurred during machining.
The present invention proposes an improved tool management method of forecasting the life of a tool with good accuracy in a simulation level before real machining and preventing tool damage and chipping from arising.
The present invention is intended to solve the problems described above, and comprises the steps of extracting tool information and cutting condition information from an NC program, obtaining cutting status information from a machining simulation based on the NC program, actually measuring tool wear at the time of actual cutting, and creating a tool wear database in which a tool cutting length and the tool wear are associated based on the information obtained from each of the steps described above.
Further, the present invention comprises the steps of extracting tool information and cutting condition information from an NC program, obtaining cutting status information from a machining simulation based on the NC program, measuring the surface roughness of an actually cut workpiece, and creating a tool wear database in which a tool cutting length and the tool wear were associated based on the information obtained from each of the steps described above.
Furthermore, the present invention comprises the steps of extracting tool information and cutting condition information from an NC program, obtaining cutting status information from a machining simulation based the NC program, actually measuring tool wear during actual cutting, creating a tool wear database in which a tool cutting length and the tool wear are associated based on the information obtained from each of the steps described above, and estimating the tool wear at the time when the relevant machining was performed using the tool wear database before actual machining is performed.
Moreover, the present invention comprises the steps of extracting tool information and cutting condition information from an NC program, obtaining cutting status information from a machining simulation based of the NC program, actually measuring tool wear at the time of actual cutting, creating a tool wear database containing a tool cutting length and the tool wear based on the information obtained from each of the steps described above, estimating the tool wear at the time when the relevant machining was performed using the tool wear database before actual machining is performed, and granting permission for actual machining by comparing the estimated tool wear and the tool life database.
As described above, according to the present invention, waste of a tool is suppressed by extending the life of the tool as far as possible, and improvement in productivity due to reduction of defective work caused by tool damage during machining and improvement in quality due to consistency of surface roughness can be promoted.